The invention is directed to new optically active 3,4-bis-(diphenylphosphino)-pyrrolidines, rhodium complexes containing them as chiral ligands and their use as catalysts for the homogeneous asymmetric hydrogenation of unsubstituted or .beta.-substituted .alpha.-acylamino-acrylic acids.
There are known from Yatagai, Chemistry Letters (1983) pages 1203 to 1206 optically active pyrrolidine derivatives of the formula ##STR2## in which Ar is a phenyl group or a methoxyphenyl group and R is an alkyl group or an .omega.-dimethylaminoalkyl group. These pyrrolidine derivatives can serve as chiral ligands in rhodium complexes, which catalysts are recommended for the asymmetric hydrogenation of dehydrodipeptides. In the asymmetric hydrogenation of .alpha.-acetamidocinnamic acid, however, the stereoselectivity of these known rhodium complexes is only slight and consequently also only low optical yields are produced.